The heat wave at the bottom of the sea

The unprecedented heat wave at the bottom of the sea has scientists around the world scrambling to understand its causes and long-term impacts. With temperatures soaring in the deep ocean and a multitude of unknowns posed by the event, it’s clear that further research is needed to understand and prevent similar phenomena in the future.

It doesn’t just stop in surface waters. It also happens in the deep ocean. A study in the journal Nature Communications studied the continental shelf surrounding North America. And it found the heat wave at the bottom of the sea.

“We studied marine heat waves at the sea surface for more than a decade.” Says Dillon Amaya, a research scientist at NOAA’s Physical Sciences Laboratory. “This is the first time we’ve been able to really dive deeper.”

This undersea heat wave was discovered near North America.
This undersea heat wave was discovered near North America.

Heat that lasts

Marine heat waves dramatically impact the health of ocean ecosystems around the world. They disrupt the productivity and distribution of organisms as disparate as plankton and whales. Temperature extremes are often studied at the ocean surface. Analyses are simpler there.

About 90% of the excess heat from global warming has been absorbed by the ocean. This has warmed by about 1.5 °C over the last century. Marine heat waves have become 50% more frequent over the last decade. But the bottom waters have now been targeted.

The research team studied continental shelves around North America. There, bottom marine heat waves tend to persist longer than their surface counterparts. There are larger warming signals than the overlying surface waters. Bottom and surface marine heat waves can occur at the same location. Especially in shallower regions where surface and bottom waters mix.

The seafloor heat wave modifies the ambient environment.
Seafloor heat wave modifies environmental setting.

Changing environment

But seafloor heat waves can also occur without evidence of warming at the surface. This affects the management of commercially important fisheries. “That means it may be happening without fisheries managers realizing it until the impacts start to be noticed,” Amaya said.

The seafloor heat wave changes the environmental setting. Increasing the frequency with which it occurs can transform the seascape…and the climate. Even more.

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